In flying an aircraft, pilots are often required to compose and send messages either to other systems on the aircraft or to systems on the ground. For example, pilots and air traffic controllers can communicate using Controller Pilot Data Link Communications (CPDLC) messages. In particular, situations arise where the pilot must request clearances or deviations to the flight plan due to weather, aircraft performance, or fuel constraint through CPDLC downlink request messages. A flight plan generally includes basic information such as, but not limited to, departure and arrival procedures, approach procedures, waypoints along the planned route that the aircraft will fly, alternate routes, estimated time en route, alternate airports, number of people on board, endurance and information about the aircraft itself. In general, different types of requests will be made to Air Traffic Control (ATC) through a CPDLC data link for clearances or deviations. These can include vertical clearances, crossing constraints, lateral route deviation, and speed changes. Additionally, messages and clearances can be received from the ground requiring action or response from the pilot.